Thanks Fred and Jim.

Fred, When I was a puppy, I run a belted centerless grinder for small round parts in a production shop and I recognize those flat spots. If the part slowed down or stopped it was ugly. I can see where the interupted area around the ejection or mag port could cause the regulating wheel to not do its job....if that is in fact the process they use. I was talking more about the flatspots right at the juncture between the face of the action and recoil lug. Almost like the force was applied right there. Kind of like a hammer peened it but flatter. It might be what you stated though or even something else. I had seen them an more than one action.

Jim, Thanks for the clarification on the other photo. That good stuff!( does anyone have that)